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VOL. 8 | NO. 48 | Saturday, November 21, 2015

Google’s Challenge Accepted

Small power inverter a big hit for UT professors, grad students

By Vicky Travis

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When Google offered its “Little Box Challenge” to the scientific world about a year ago – asking inventors to make the smallest, most efficient two-kilowatt inverter possible – Daniel Costinett was intrigued.

A University of Tennessee engineering professor, Costinett, kicked the idea around with a team of graduate students.

The Electric Power Research Institute, an independent nonprofit, would soon collaborate, and after thousands of hours building and testing their efficient tiny box, the UT team had its entry.

It is one of 18 finalists worldwide.

“I fortunately had this great group of students,” Costinett says. “Many times I’d be down in lab until 1 a.m., and students were there with me.

“There were plenty of weeks when we put in around 100 hours a week. The level of drive and commitment was great.”

Go small or go home

In the end, UT’s inverter is about the size of a pack of medium-size index cards. Many household inverters, like those used with a solar panel, are about the size of a picnic cooler, according to Google.

Finalists had to deliver their inverter prototypes for testing at the National Renewable Energy Laboratory in Golden, Colorado, in October.

Of the 15 teams able to deliver a prototype, the UT team is one of only three from the U.S.

Now, the wait: The $1 million winner will be announced in January, after the prototypes go through 100 hours of testing.

Win or not, both UT and EPRI engineers were happy with their discoveries and will continue to refine the small inverter – something that eventually could improve efficiency, cost and portability of electricity used in military, space, developing world and renewable applications.

Dr. Fred Wang, Brad Trento, Dr. Daniel Costinett, Chongwen Zhao, Bo Liu and Ling Jiang. Below, the inverter.

(Chase Malone/The Ledger)

The team

Along with Costinett, the UT team included professors Leon Tolbert and Fred Wang and graduate students Chongwen Zhao, Brad Trento, Ling Jiang, Bo Liu and Zheyu Zhang, who graduated during the competition and is now a research professor at UT.

Enter the Electric Power Research Institute, a non-profit focused on making electricity more reliable, affordable and environmentally friendly. Its Knoxville facility is about 15 miles from UT.

“Our industry needs inverters,” explains Rick Langley, EPRI’s project leader.

“We did a study in 2010 and convened experts and identified six needs. In looking at this Google Challenge, it addressed three of the six needs. We thought it would match up well.”

The three needs the challenge addresses are improved component packaging and mechanical design, enhancement in thermal management and high-efficiency power conversion.

“What happened was an incredible meshing of talents there and here,” says Langley of UT’s team and EPRI engineers John Jansen and Reid Kress. “We learned a lot about circuits and they learned about thermal managing.”

“This was an opportunity to make an impact,” he adds. “We funded UT to help them in the contest. When we came on board, it helped to free up additional resources, faculty and students.”

“I’m glad we did this though it was hard to feel that way in the middle,” admits Trento, UT doctoral student.

“Given the time frame, we were happy with where we got it and always ensured it was reliable.”

A year is a quick turnaround for a big project like this, so the team plans to build two more little boxes for further research, one for UT and one for EPRI.

Google owns none of the intellectual rights.

“We want to dig deeper into issues we found,” Trento says.

“A variety of technical problems have been our headache through the whole project, but we succeeded to find out ways to solve them, with support from EPRI and our research center,” says Zhao, who is also pursuing his doctorate at UT.

“The biggest challenge for me in the second phase of the project, the prototype building stage, was to overcome frustrations brought by numerous prototype failures.

“Keeping positive towards those failures enabled us to build a high-performance inverter and be a finalist.”

“The biggest challenge for me in the second phase of the project, the prototype building stage, was to overcome frustrations brought by numerous prototype failures,” said Chongwen Zhao, shown here tinkering with the inverter.

(Chase Malone/The Ledger)

The big deal about small

Like most things electrical, most of us don’t consider them until, say, our phones run out of juice. Plug a phone in and the alternating current converts to direct current stored in the phone battery.

The Google Little Box Challenge prompted engineers to shrink an inverter, which takes current the opposite direction – direct current (as in a battery) changes to alternating current (like we use in our homes every day). And, just as cell phones have slimmed down over the years, smaller inverters could potentially mean less cost to create, transport and more.

“Anywhere the grid isn’t available, you could potentially take it and make AC power from a DC source,” explains Langley.

“Smaller and lighter means it’s good to transport out somewhere.”

A number of projects in the developing world do this already, he adds.

Think of space, the military and developing world applications. “All of those things absolutely make sense,” Langley says.

And renewable energy – solar, wind and hydro power – needs inverters.

“The sun is not always shining, so we have to develop tools to use it,” adds Langley.

It’s physics. Once generated, electricity has to go somewhere – either it’s used, it’s stored (like a battery) or it’s dumped.

So, the challenge for today’s electrical engineers is finding ways to store renewable energy and efficiently deliver it for people to use. It would be logical that the smaller and lighter an inverter can be, the better.

“Our grid we live with today is not designed with renewables in mind,” explains Langley. “Grid operators need real time control over renewables.”

Some pilot studies are combining large grid systems with battery-stored energy, he notes.

During the Google competition, the team had to meet deadlines and a list of requirements, including keeping the device under 60 degrees.

“As you start shrinking these things down, there’s no room for big fans,” Costinett says.

To make it smaller, the team tried stacking components different ways, using flexible printed circuit boards and creating some components on a 3D printer.

Then, they tested and tested again for reliability.

“We will continue working with the prototype,” Costinett adds.

“There are a lot of things to investigate, and on a larger scale, there’s a lot of research here to make these things better, lighter, and higher performance.”

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